Synthesis gases are hydrogen-containing gas mixtures which are employed in various synthesis reactions. Examples include the methanol synthesis, the production of ammonia by the Haber-Bosch process or the Fischer-Tropsch synthesis.
A commonly used process for producing synthesis gases is the autothermal entrained-flow gasification of gaseous, liquid or solid fuels, as it is described for example in DE 10 2006 059 149 B4. At the head of a reactor, an ignition and pilot burner as well as rotationally symmetrically to the reactor axis three gasification burners are centrally arranged. Via the gasification burners, coal dust with oxygen and steam as gasification medium is supplied to a gasification space of the reactor, in which the fuel is converted to synthesis gas. Along with the liquid slag, the hot gasification gas leaves the gasification space and gets into a quenching space, into which water is injected for cooling raw gas and slag. The slag is deposited in the water bath and is discharged via a slag outlet. The quenched raw gas saturated with steam is withdrawn from the quenching space and cleaned in succeeding cleaning stages.
Since the fuel is directly reacted with the oxidizing agent, oxidizing agent and fuel must be supplied coaxially and coannularly.
U.S. Pat. No. 5,549,877 A1 also describes a process and an apparatus for producing synthesis gas, wherein an oxygen-containing oxidizing agent is centrally supplied at the reactor head and introduced into the reaction space along with fuel supplied annularly around the oxidant supply, in which reaction space the fuel initially is reacted substoichiometrically. There is formed a flame which advances downwards into the reaction space. In a recirculation zone, the materials present in the flame flow back to the top. Downstream via an annular conduit, an additional stream of oxidizing agent is supplied into the reaction zone, so that a flame zone expanded further is formed.
DE 10 2006 033 441 A1 describes a reformer for a fuel cell system, in which fuel is introduced into an oxidation zone through a centrally arranged fuel supply and in addition an oxidizing agent, in particular air, is introduced via oxidant supply means provided vertically thereto. Inside the oxidation zone, a reaction of fuel and oxidizing agent takes place by combustion. The product gas obtained then enters into a downstream mixing zone, in which fuel and oxidizing agent additionally are supplied by means of a secondary fuel supply means. The product gas mixed with the additional fuel enters into a reformation zone, in which it is converted into a gas mixture rich in hydrogen by an endothermal reaction, which gas mixture is withdrawn and provided to a fuel cell stack.
The arrangement of a burner in the head of a reactor, in which the oxidizing agent and the fuel are jointly supplied to the reactor, has the disadvantage that a strong flow is formed along the reactor axis. This flow is particularly large when liquid fuels are gasified. Due to the high relative velocity of fuel and atomizing medium still inside the burner or in the succeeding reaction space, the entry momenta of the media in direction of the reaction space axis are very high. The consequence is that the residence time along the reactor axis is very short, so that either a long reactor is required or the desired degree of conversion cannot be achieved. What is also disadvantageous is the larger diameter of the burner, which due to the large number of media outlets requires a large flange at the reactor. In addition, the coannular media arrangement frequently influences the mixing of the media in a disadvantageous way. In particular in the reformation of liquids, the spray cone of the liquid droplets can be constricted by the enveloping media with this arrangement.
To avoid the resulting unfavorable residence time distribution, the use of a plurality of burners therefore has been proposed already, whose flame zones partly overlap or deflect each other in the reaction space. As a result, the technical effort for the supply of media is increased, since each burner requires at least two inlets for fuel and oxidizing agent as well as possibly moderator and cooling water connections. For the exact regulation, an additional separate measuring and regulation technique also is required. Finally, the failure probability of the reactor increases corresponding to the number of burners.